Development of copper-free eco-friendly brake-friction material using novel ingredients

• Usage of Cu in friction material (FMs) is almost banned in advanced countries.
• Efforts were made to replace Cu using novel conducting rock-fibers and thermographite.
• Cu-free FMs were developed and proved quite successful.
• The exact performance matching can be done in future by few more trials.
• Interestingly thermal conductivity of new FMs was higher than that of Cu-based FM.

Historically, copper (Cu) and its alloys have played a vital role as additives to non-asbestos friction materials (FMs). Their main functions include; to increase thermal conductivity, to act as a solid lubricant at high temperature, and to influence general tribological performance. Environmental concerns in most of the advanced countries have resulted in legislation to gradually phase out the use of Cu in FMs. Thus, the FM Industry is facing a challenge to replace Cu and its alloys in FMs with additives that will match the desired performance. The goal of this work was to test the potential of two new FM fillers (conductive rock-fibers and thermo-graphite-TG) on a brake dynamometer using standard test schedule (JASO 406). Five brake-pad materials, comprising two series, were developed with identical parent compositions. The first series called Copper Based (CB) consisted of two FMs with and without untreated Rockwool (RB) and natural graphite (NG). The second series designated as Copper-Free (CF) series contained three FMs with increasing wt% of rock fibers (10%, 15% and 20%), along with 10% TG. Physical and mechanical properties of the compression-molded pads were measured. Cu-based FM performed better than the Cu-free FMs, but not significantly in most of the important properties. For certain other properties, Cu-free FMs performed better.